verb

(of fabric) fill with air and swell outward.

her dress billowed out around her

puff out,puff up,balloon,balloon out,swell,fill out,bulge out,belly out

noun

A large undulating mass of something, typically cloud, smoke, or steam.

Flying in across a track of pearl and gold laid by the setting sun across the Atlantic, I watched the island shape itself as a dark mass hardening from a billow of pink sea-level clouds.

cloud,mass